<html>
 <head>
   <title>Hello World</title>
 </head>
 <body>
  <form action="/index/vali" method="post">
    <p><input type="text" name="data[username]" value="<?php form_old('username');?>" placeholder="用户名"></p>
    <?php form_error('username');?>
    <p><input type="text" name="data[password]" value="<?php form_old('password');?>" placeholder="密码"></p>
    <?php form_error('password');?>
    <p><input type="submit" value="提交"></p>
  </form>
 </body>
</html>